This invention relates to door lock assemblies and particularly to a door lock having a mechanically actuated automatic deadbolt lock with door closure.
Crime rate increases beginning particularly in the 1950's caused widespread adoption of deadbolts in door lock assemblies. Typically such an assembly included a latch which is depressed during closure of the door and, with substantially complete closure, extends into a recess of the door strike. Such a latch by itself is often easy to improperly depress-release by an unauthorized person, with a card-type element or even a pry bar. Also the outer knob assembly can be torqued off with a wrench to gain access to the mechanism and thereby to the room closed by the door. Deadbolts are not as susceptible to these unauthorized activities. Doors having deadbolts also typically use a latch mechanism. This is because (1) the latch holds the door snug against rattling whereas the deadbolt by necessity must have clearance between it and the stroke plate recess edges (but because of that clearance, the door can rattle), and (2) the latch automatically holds the door shut since it is only momentarily depressed during door closure from its normally extended condition and then extends into a door strike recess when the door is fully closed.
Except in rare devices where the deadbolt is operated by an electrical solenoid, the deadbolt, to be effective, must be manually thrown by a person inside the room or building, or if the deadbolt is actuable by an external key, the person leaving the room or building must purposely engage the deadbolt by a key as the person leaves. However, if a person forgets to so actuate the deadbolt, either manually with an inner hand turn when inside, or by a key when outside, an intruder need only inactivate the latch mechanism in order to gain unauthorized entry. Motel and hotel rooms often do not even have a key actuated deadbolt and thus are particularly susceptible to unauthorized entry and theft when the person is not in the room.
In recent years, mechanisms such as that in U.S. Pat. No. 3,999,789 were developed to enable retraction, i.e. inactivation, of the deadbolt simultaneously with the latch for quick release even under panic exit conditions. But to lock the door still required manual actuation of the deadbolt with the inner hand turn or a key on the outside.